The present invention relates to a shade matching apparatus for porcelain crowns that need special characteristics in shading, and also relates to a method of matching a porcelain crown to the natural teeth by relying on the human eye, and not a computer shading system of some sort.
This solution represents an advance relative to the use of any conventional shade guide. A commercial shade guide has a plurality of colors in a single uniform shade whereby no special characteristics are indicated.
Such a shade guide has limited selection options. This limitation is not due lack of options for combining different shades, but rather the fact that most natural teeth has special characteristics that would require additional staining in certain parts of a tooth. This special staining can be achieved easily by simply adding special stains to the selected base shade in a standard shade guide during the firing process. The problem with that is most dentists do not have the stain or are not trained in determining what color of stain could be used for better results.
An additional problem is that in order to achieve a more life-like appearance by adding special stains a dentist is usually limited to the options available. A practitioner would either have to send the patient to the lab, which is usually inconvenient for the patient, or the lab might come to the dentist office, which is usually inconvenient for the lab as well as the dentist.
Another option for shading is a computerized shading system of some sort, and these systems have limitations that usually produce an unsatisfactory result. Although a computerized system can and usually finds different shades in a tooth, they are programmed to select said different shades from the colors in a standard shade guide. For example, if a natural tooth has a chroma shade at the cervical or a translucent shade at the incisal the computer will pick a shade from the conventional shade guide that is the closest match to that. A standard shade guide does not include shades that are translucent or chromatic, therefore the shade selected likely will not match correctly.
Another problem is that with a computerized system a practitioner or libratory technician places the handpiece of the system directly against the tooth, and the computer can not take into account the different factors that may need to be noted in determining the shade, such as a persons skin tone or the shape, size and color of the patients lips, which sometimes play a big part in determining the shade of an anterior tooth.